Snapping elbow is a rare condition, which has various possible causes such as impinged plica, annular ligament, or other extra-articular causes. We report a case of 15-year-old boy who had snapping elbow and sudden-onset flexion contracture of the elbow. Simple radiographs showed bilateral anterior dislocation of hypoplastic radial heads. Magnetic resonance images with the elbow extended as much as possible showed that the annular ligament hemmed the dislocated radial neck. By surgical incision of the annular ligament which checkreined the radial neck, the patients could regain full extension of the elbow. We recommend careful consideration of surgical excision of ligamentous structure which blocks extension in the patients who have history of snapping elbow with congenital radial head dislocation.